arm/usr/arm-none-eabi/include/machine/endian.h

#ifndef __MACHINE_ENDIAN_H__

#include <sys/config.h>

#ifndef BIG_ENDIAN
#define BIG_ENDIAN 4321
#endif
#ifndef LITTLE_ENDIAN
#define LITTLE_ENDIAN 1234
#endif

#ifndef BYTE_ORDER
#if defined(__IEEE_LITTLE_ENDIAN) || defined(__IEEE_BYTES_LITTLE_ENDIAN)
#define BYTE_ORDER LITTLE_ENDIAN
#else
#define BYTE_ORDER BIG_ENDIAN
#endif
#endif

#endif /* __MACHINE_ENDIAN_H__ */